本文關(guān)鍵詞：認(rèn)知無線網(wǎng)絡(luò)中基于頻譜態(tài)勢(shì)的頻譜接入方法研究　出處：《重慶郵電大學(xué)》2016年碩士論文　論文類型：學(xué)位論文

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【摘要】：在認(rèn)知無線網(wǎng)絡(luò)中,頻譜態(tài)勢(shì)是無線頻譜資源在時(shí)-頻-空域的當(dāng)前狀態(tài)和未來趨勢(shì),反映當(dāng)前頻譜特征,是動(dòng)態(tài)頻譜接入的重要依據(jù)。本文通過分析時(shí)-頻-空域上的頻譜態(tài)勢(shì),研究小尺度認(rèn)知無線網(wǎng)絡(luò)和大尺度認(rèn)知無線網(wǎng)絡(luò)下的頻譜接入問題。主要研究內(nèi)容有:在小尺度認(rèn)知無線網(wǎng)絡(luò)中,次用戶(SU)間的距離比較近,網(wǎng)絡(luò)半徑較小,不同SU感知到的頻譜態(tài)勢(shì)相似,SU主要通過時(shí)間和頻率上的頻譜空洞進(jìn)行頻譜接入。本文提出基于信道時(shí)-頻態(tài)勢(shì)的混合頻譜接入方法,通過兩狀態(tài)馬爾科夫過程對(duì)信道狀態(tài)進(jìn)行建模,估計(jì)信道在時(shí)間和頻率維度的狀態(tài),SU根據(jù)信道狀態(tài)選擇Overlay或者Underlay接入方式,然后以最大化系統(tǒng)容量為準(zhǔn)則求解SU最優(yōu)發(fā)射功率,并通過修正信道轉(zhuǎn)移概率來降低頻譜感知誤差的影響。理論分析和仿真實(shí)驗(yàn)表明,本文方法下的認(rèn)知系統(tǒng)容量優(yōu)于單一的Overlay或Underlay系統(tǒng)。頻譜態(tài)勢(shì)圖可以有效地估計(jì)不同地點(diǎn)的干擾和空白頻帶,指導(dǎo)不同位置的SU進(jìn)行頻譜接入和功率控制。針對(duì)傳統(tǒng)插值法構(gòu)建頻譜態(tài)勢(shì)圖精度較低而且所需測(cè)量節(jié)點(diǎn)較多的問題,本文提出基于主用戶(PU)信息構(gòu)建頻譜態(tài)勢(shì)圖的方法,針對(duì)PU發(fā)射功率未知的情況,首先基于接收信號(hào)強(qiáng)度利用最小二乘法建立定位模型,然后利用拉格朗日乘數(shù)法求解PU的位置和發(fā)射功率,最后根據(jù)PU空間信息和傳播模型直接構(gòu)建頻譜態(tài)勢(shì)圖。實(shí)驗(yàn)表明本文方法比傳統(tǒng)的空間插值法構(gòu)建頻譜態(tài)勢(shì)圖精度高而且所需測(cè)量節(jié)點(diǎn)數(shù)少。在大尺度認(rèn)知無線網(wǎng)絡(luò)下,SU網(wǎng)絡(luò)半徑較大并且分布較廣,離PU較遠(yuǎn)的區(qū)域可能不存在PU的影響,空間頻譜空洞由此產(chǎn)生。本文提出基于位置信息的空間頻譜接入方法,首先分析主網(wǎng)絡(luò)覆蓋范圍、主次用戶之間距離以及認(rèn)知網(wǎng)絡(luò)容量之間的關(guān)系,然后根據(jù)主次用戶的三種位置關(guān)系進(jìn)行功率控制,解決主次用戶在空間上并發(fā)通信的干擾問題,指導(dǎo)不同位置的SU進(jìn)行頻譜接入。在保證PU正常通信的情況下,為SU提供更多的空間頻譜接入機(jī)會(huì),提升認(rèn)知系統(tǒng)的容量。
[Abstract]:In cognitive wireless networks, spectrum situation is the current state and future trend of wireless spectrum resources in time-frequency-spatial domain, reflecting the current spectrum characteristics. It is an important basis for dynamic spectrum access. This paper analyzes the spectrum situation in time-frequency-spatial domain. In this paper, the spectrum access problem in small scale cognitive wireless networks and large scale cognitive wireless networks is studied. The main research contents are as follows: in small scale cognitive wireless networks, the distance between secondary users is close. Because the radius of the network is small and the spectrum situation of different Su is similar, the spectrum access is mainly carried out through spectrum holes in time and frequency. A hybrid spectrum access method based on channel time-frequency situation is proposed in this paper. The channel state is modeled by two-state Markov process, and the channel state in time and frequency dimension is estimated. According to the channel state, the Overlay or Underlay access mode is selected. Then, the optimal transmit power of Su is solved by maximizing the system capacity, and the influence of spectrum sensing error is reduced by modifying the channel transfer probability. The theoretical analysis and simulation results show that. The capacity of cognitive system under this method is better than that of single Overlay or Underlay system. The spectrum situation map can effectively estimate the interference and blank frequency band of different locations. To guide the Su in different positions to access spectrum and control power. Aiming at the problems of low precision and more measurement nodes needed to construct spectrum situation map by traditional interpolation method. In this paper, a method of constructing spectrum situation map based on primary user information is proposed. In view of the unknown transmission power of pu, the location model is established based on the received signal strength using the least square method. Then the Lagrange multiplier method is used to calculate the position and power of pu. Finally, the spectral situation map is constructed directly according to pu spatial information and propagation model. The experimental results show that the proposed method is more accurate than the traditional spatial interpolation method and requires less points of measurement nodes. Under the network. Due to the larger radius and wider distribution of Su network, there may be no pu effect in the region far away from pu, and the spatial spectrum cavity may be generated. In this paper, a spatial spectrum access method based on location information is proposed. Firstly, the relationship among the main network coverage, the distance between the primary and secondary users and the cognitive network capacity is analyzed, and then the power control is carried out according to the three position relationships of the primary and secondary users. In order to solve the interference problem of concurrent communication between primary and secondary users in space, and guide the Su in different locations to access the spectrum, we can provide more access opportunities for Su in the case of normal communication of pu. Increase the capacity of the cognitive system.
【學(xué)位授予單位】：重慶郵電大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：TN925

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本文編號(hào)：1407087